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I need some graphic design advice on finding a quotable piece of information regarding the use of "highlighting" text on signage, which I hope you can help me with.

I'm in a dispute with my local council about a parking sign where they have put some vital information about the charging period which the have "highlighted" on a sign with a generally white background by using black text on a grey background. Common sense tells me that this low contrast combination of black text on a grey background is not a "highlighting" strategy, but rather obscures the text instead. Unfortunately my local council has no common sense, so I need to justify my "crackpot" theory with a reference to some respected source, such as a typographical text book or learned paper.

Can anyone point me in the direction of such a reference I could quote in my defence? Many thanks in anticipation of your support.


Thanks for your answers and apologies to those of you who think my question is more legal than graphic. I'm new to the site and have no intention of offending anyone or breaking the rules.

I have posted a picture on iCloud of the sign:


The picture was taken at night, so the obscuring effect of the grey background is even worse in my opinion. Would you think that the "evening charges apply" text is readily visible?

I will go take a picture in daylight and try to get an accurate idea of the grey level, to use the "Arthur and Passini" contrast calculation kindly referenced by Yisela.

Many thanks again for your input and help, it's very much appreciated by me.


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@Scott I disagree. While the context is legal, the question itself can't be more design related. Paul, do you have a picture of the sign you can share? I think it will all depend on much contrast there is between the black and the grey. –  Yisela Feb 3 at 20:14
Definitely on target. For me, particularly as I'm working on a website for the visually impaired, the issue of contrast is very relevant to readability and design. –  Ray Mitchell Feb 3 at 20:16
Contrast yes, but something which states "black on grey is not a highlight" won't be found. –  Scott Feb 3 at 20:19

2 Answers 2

I am not sure you will be able to talk about "highlighting" of information, as it doesn't really define anything by itself. What is a highlighted element? Maybe something that needs to be made clear in comparison to other information. The argument could get too vague. How about you go for readability instead? In the first case, your argument should have to be "I didn't notice that part of information was important". In the second, "I didn't consider the message, because I never really noticed it".

One of the main influences of readability is contrast. Arthur & Passini described in their book Wayfinding from 1992 a reliable method to calculate the contrast difference between two colors:

The formula is based on the light reflectancy (LR) readings in percentages for each of the two colors involved. By substracting the darker color from the lighter color, divided by the difference by the lighter, and multiplying by 100, we get brightness differential. When the brightness differential is 70 percent or higher the legibility is assured. When it is less, the legibility cannot be assured and those colors should not be using in that combination.

I don't know how grey your grey was, but if you could get a low differential that could certainly help. It would probably also be relevant that the reference is about architecture, graphics and verbal human interaction.

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Light reflectancy values are actually measured in 'real life', so if you need to do a digital calculation you can use Lea Verou's amazing Contrast Ratio calculator.

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I agree with Scott that you will not get a bunch of designers behind you on "black on gray is not a highlight", waving placards. I think @Yisela pinpoints it: you can use solid signage design principles and argue that, with solid backup. Wether they will listen is another kettle of fish: the world is full of idiots. –  Random O'Reilly Feb 3 at 21:53
Solid, I agree highlighting is just a keyword that you could stumble on. The issue is certainly readability. –  Jenna Feb 3 at 21:56

This is really a legal matter. Black text on grey may indeed be a highlight. It all depends on the value of grey and other surrounding elements. I doubt you'll find anything specifically stating black on grey is NOT a highlight. In fact, in web design, black on grey is used often to highlight areas.

Look here: Bootstrap, a very widely used Twitter architecture, uses black on grey as a highlight.

Even here on Stack Exchange sites....

Black text on a grey background is used to highlight content.

Sorry, I think you'll lose the argument. But... I'm no lawyer.

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Yes, this is a key point. Context is important here. To highlight essentially means to emphasize, and that an be done any number of ways...provided it is significantly different than the rest. –  DA01 Feb 4 at 2:32

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